The technology of MEMS (micro-electro-mechanical systems) is related to devices comprising an electronic part which may be fabricated using integrated circuit (IC) process sequences, and comprises a micromechanical component which is usually fabricated using compatible “micromachining” processes that selectively remove (for instance etch away) parts of a semiconductor (for instance silicon) wafer and/or that add new structured layers to form the mechanical and electromechanical devices.
Zook, J D, Herb, W R, Ahn, Y and Guckel, H, “Polysilicon sealed vacuum cavities for microelectromechanical systems”, J. Vac. Sci. Technol. A 17(4), July/August 1999 discloses sealed vacuum cavities used in silicon-based micro-electro-mechanical systems. Sealed polysilicon cavities may serve as reference chambers for pressure sensors and provide enclosures for high-Q mechanical resonators. Optically resonant microbeams are potentially suitable for fibre optic based sensors that withstand harsh environments, including high temperature. Zook et al. 1999 thus discloses a polysilicon vacuum cavity formed by reactive sealing. Depositing a polysilicon layer on top of a sacrificial layer may form a cavity. A pattern of a thinner sacrificial structure is used as an etch channel. After the material of the sacrificial layer is removed, the reactive sealing is done with SiH4. The SiH4 decomposes, leaving only hydrogen that diffuses out through the silicon, leaving a hard vacuum.
However, the procedure of forming polysilicon sealed vacuum cavities of Zook et al. may be complex and may lack reliability.